Unfortunately, there is not a lot of data available regarding how certain inactive ingredients may affect individuals when changing manufacturers of a drug.
The first thing you should to is make sure you do not have a known allergy to any one of the ingredients, namely the dyes/coloring. Allergies to dyes are the biggest reason why one manufacturer of a generic medication may cause adverse reactions in someone.
Prescription Drug Inactive Ingredients
You may notice that almost all generic manufacturers use different inactive ingredients in their products. If you have 10 different manufacturers of a product, you will most likely find 10 different lists of ingredients. There are many reasons for this.
First and foremost, generic drugs cannot look like the brand name drug (unless the generic is 'authorized', which is a different story). Unknown to most people, brand name manufacturers have a patent not only on the formula of a drug but also the look of the drug. Also, different manufacturers use specific equipment in their facilities, which is often calibrated for the specific ingredients that the manufacturer most commonly uses. Lastly, many manufacturers tend to make all their generics have a certain look to them, which requires specific inactive ingredients.
Aside from allergies, you may have to just try the new prescription manufacturer and see how it affects you. You could also ask the pharmacy you go to if they are able to source the original product you were taking.
Why Do Pharmacies Switch Generic Brand Manufacturers?
There could be many reasons why your generic manufacturer was changed including supply issues, price and availability from suppliers. It is worth asking if you could switch back. You could always call around to other pharmacies and see if they have the product available. It's not uncommon that different pharmacies carry different manufacturers, even pharmacies within the same chain.
Brand Vs. Generic Medications
There are also concerns regarding whether or not generic drugs have the same effect of the brand name, or if different manufacturers are interchangeable. The key point to note is that the active ingredient in all the generic products is exactly the same as the active ingredient in the brand name drug.
In addition, both the rate and extent of absorption needs to be the same between all manufacturers of the drug (technically, studies need to show that all version of the drug are within the statistical range of 80% to 125% of the brand product... which amounts to no more than 3% to 4% difference in how the drug is absorbed in the body). This is referred to as pharmaceutical equivalence, or bioequivalence.
So again, we unfortunately cannot give you any indication regarding how you will react to the new manufacturer of your generic drug, as everyone is different. If you are concerned however, talk to your pharmacist,or other pharmacies, as we discussed above.